Geothermal heat pump for a small single-story single-family house

Is there a guide or literature on which heat pump would be best suited for such a small construction project? Thank you.

It is not only about the size of the house but especially about good insulation and thus a low H,T value (transmission heat loss). The better the H,T value, the lower the heating load of the house. So a poorly insulated house with 120 m² can have a greater heating load than one with 160 m² that is well insulated. Search for Trenchplanner and Grabenkollektor on Google. With this tool, you can calculate your approximate heating load based on the house data and the H,T value. Only then can it be said whether an air-water heat pump can efficiently heat your house. Alternatively, you can also provide the following values of your house, then we can discuss directly here and the heating load will be more comprehensible for everyone.

H,T value
desired average temperature
envelope area (A)
heated gross volume (Ve)
ventilation (controlled residential ventilation, decentralized, window ventilation)

We built a ground source heat pump with a ring trench collector on a 410 m² plot (160 m² heated area), and it worked without any problems. So it doesn’t always have to be a deep borehole.

Regarding funding: As far as I know, funding for energy-efficient heat pumps was discontinued at the end of 2020. That means the additional cost for a ground source heat pump would have to be weighed against possible increased heating costs for an air-water heat pump. If you provide your own labor, then a ground source heat pump does not cost significantly more than an air-water heat pump (about 3,000 euros if a ring trench collector is built).

Procedure: 1. Insulation -> Has the greatest impact on heating costs 2. Design of the underfloor heating -> If something is done wrong here, it affects the efficiency of the heating 3. Heat generator -> Heat pump, gas heating can all heat effectively, here it depends on what one personally expects regarding future energy prices.

Recommendation: Calculation of the heating load room by room according to DIN, specifying the desired temperature for each room. Have the design of the underfloor heating calculated by a specialist office, costs a few hundred euros but usually brings the best results.

Cover a large area in the bathrooms and use small distances, possibly wall heating.

Dimension the connection to the HKV large enough so that enough reaches the upper floor.

Heat generator Heat pump: modulating with the lowest possible minimum output, maximum output not greater than the calculated heating load. BWT: smallest possible minimum output (1.8 to 3 kW) maximum output not greater than the calculated heating load.

I would not consider a "must" for the comparison (commercial calculation of the options) as given. What do you want? What can you afford? (I mean: no one has to be the richest person in the cemetery ...) And consider the total resource requirements (acquisition, operation) as far as possible, taking into account the desired comfort. Try to understand the basic differences, then you can decide better and say what you "feel comfortable" with.

Thank you very much for the answers, I can already make use of that.